The present invention relates to a silver halide photographic material, and particularly to a photothermographic material.
In the recent medical diagnostic film field and photomechanical film field, it has been eagerly desired to reduce the amount of processing waste fluid, from the viewpoints of environmental preservation and space saving. Accordingly, techniques relating to photothermographic materials have been required as medical diagnostic films and photomechanical films which can be efficiently exposed with a laser image setter or a laser imager and can form sharp black images having high resolution. These photothermographic materials can dispense with the use of processing chemicals of the solution system, so that they can provide to customers heat development processing systems which are simpler and do not damage the environment.
There is also a similar demand in the field of general image formation materials. However, images for medical diagnosis particularly require fine depictions, so that high image quality excellent in sharpness and graininess is necessary. Moreover, they are characterized by that blue black tone images are preferred from the view point of ease of diagnosis. At present, various kinds of hard copy systems utilizing dyes or pigments, such as ink jet printers and electrophotogarphy, are in circulation as general image formation systems. However, they are not satisfactory as output systems of medical images.
On the other hand, heat image formation systems utilizing organic silver salts are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075, and D. Klosterboer, Thermally Processed Silver Systems (Image Processes and Materials), Neblette, the eighth edition, edited by J. Sturge, V. Walworth and A. Shepp, chapter 9, page 279 (1989). In particular, photothermographic materials generally have light-sensitive layers in which catalytic active amounts of photocatalysts (for example, silver halides), reducing agents, reducible silver salts (for example, organic silver salts) and optionally color toning agents for controlling a color tone of silver are dispersed in binder matrixes. After image exposure, the photothermographic materials are heated to a high temperature (or example, 80xc2x0 C. or more) to form black silver images by the oxidation-reduction reaction between the reducible silver salts (which act as oxidizing agents) and the reducing agents. The oxidation-reduction reaction is promoted by the catalysis of latent images of silver halides generated by exposure. The black silver images are therefore formed in exposed regions. These are disclosed in many literatures including U.S. Pat. No. 2,910,377 and JP-B-43-4924 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d).
However, in the organic silver salt-containing photothermographic materials, even the use of sensitizing dyes which can absorb red laser beams has still raised problems with regard to the appearance of fog not practically negligible and changes in performance during storage, although they are alleviated by infrared dyes.
An object of the present invention is to provide a silver halide photographic material, particularly a photothermographic material, having high sensitivity, low fog and good shelf life (i.e., good storage stability).
The above-described object has been attained by the following means:
(1) A silver halide photographic material comprising at least one kind of merocyanine dye represented by formula (I) 
wherein Z1 represents an atomic group necessary for forming a naphthoxazole ring, R1 and R2 each represents an unsubstituted or substituted alkyl group, an aryl group or a heterocyclic group, L1, L2, L3 and L4 each represents a methine group, M1 represents a charge neutralizing counter ion, and m1 is a number of 0 or more necessary for neutralizing a charge in a molecule.
(2) The silver halide photographic material described in (1), wherein said merocyanine dye represented by formula (I) is a merocyanine dye represented by formula (II): 
wherein R3 and R4 each represents an unsubstituted or substituted alkyl group, an aryl group or a heterocyclic group, V1, V2, V3, V4, V5 and V6 each represents a hydrogen atom or a substituent, L5, L6, L7 and L8 each represents a methine group, M2 represents a charge neutralizing counter ion, and m2 is a number of 0 or more necessary for neutralizing a charge in a molecule.
(3) A photothermographic material having a support containing at least one kind of light-sensitive silver halide, a light-insensitive organic silver salt, a reducing agent for a silver ion and a binder in one face thereof, which comprises at least one kind of merocyanine dye represented by formula (I) or (II): 
wherein Z1 represents an atomic group necessary for forming a naphthoxazole ring, R1 and R2 each represents an unsubstituted or substituted alkyl group, an aryl group or a heterocyclic group, L1, L2, L3 and L4 each represents a methine group, M1 represents a charge neutralizing counter ion, and m1 is a number of 0 or more necessary for neutralizing a charge in a molecule; and 
wherein R3 and R4 each represents an unsubstituted or substituted alkyl group, an aryl group or a heterocyclic group, V1, V2, V3, V4, V5 and V6 each represents a hydrogen atom or a substituent, L5, L6, L7 and L8 each represents a methine group, M2 represents a charge neutralizing counter ion, and m2 is a number of 0 or more necessary for neutralizing a charge in a molecule.
(4) The silver halide photographic material described in (2), wherein R4 in the merocyanine dye represented by formula (II) is a carboxymethyl group.
(5) The photothermographic material described in (3), wherein R4 in the merocyanine dye represented by formula (II) is a carboxymethyl group.
(6) The silver halide photographic material described in (2), wherein V1, V2, V3, V4, V5 and V6 in the merocyanine dye represented by formula (II) are hydrogen atoms.
(7) The photothermographic material described in (3), wherein V1, V2, V3, V4, V5 and V6 in the merocyanine dye represented by formula (II) are hydrogen atoms.
(8) A silver halide photographic material comprising at least one kind of merocyanine dye represented by formula (II) and at least one kind of merocyanine dye represented by formula (III): 
wherein R3 and R4each represents an unsubstituted or substituted alkyl group, an aryl group or a heterocyclic group, V1, V2, V3, V4, V5 and V6 each represents a hydrogen atom or a substituent, L5, L6, L7 and L8 each represents a methine group, M2 represents a charge neutralizing counter ion, and m2 is a number of 0 or more necessary for neutralizing a charge in a molecule; and 
wherein R5 and R6 each represents an unsubstituted or substituted alkyl group, an aryl group or a heterocyclic group, V7, V8, V9 and V10 each represents a hydrogen atom or a substituent, L9, L10, L11 and L12 each represents a methine group, M3 represents a charge neutralizing counter ion, and m3 is a number of 0 or more necessary for neutralizing a charge in a molecule.
(9) The silver halide photographic material described in (8), wherein V7 and V10 in the merocyanine dye represented by formula (III) are each a hydrogen atom, and V8 and V9 therein are each an unsubstituted or substituted alkyl group.
(10) The silver halide photographic material described in (2), wherein R5 in the merocyanine dye represented by formula (II) is an unsubstituted alkyl group having 5 to 10 carbon atoms.
(11) The phot-thermographic material described in (3), wherein R5 in the merocyanine dye represented by formula (II) is an unsubstituted alkyl group having 5 to 10 carbon atoms.
(12) The silver halide photographic material described in (8), wherein R5 in the merocyanine dye represented by formula (II) is an unsubstituted alkyl group having 5 to 10 carbon atoms.
(13) The silver halide photographic material described in (2), wherein a silver halide emulsion containing the merocyanine dye represented by formula (II) is sensitized with a tellurium sensitizer.
(14) The photothermographic material described in (3), wherein a silver halide emulsion containing the merocyanine dye represented by formula (II) is sensitized with a tellurium sensitizer.
(15) The silver halide photographic material described in (8), wherein a silver halide emulsion containing the merocyanine dye represented by formula (II) is sensitized with a tellurium sensitizer.
Formulas (I) to (III) will be described in more detail below.
Z1 represents an atomic group necessary for forming a naphthoxazole ring. As Z1, naphto[2,1-d]oxazole, naphto[2,3-d]oxazole and naphto[1,2-d]oxazole rings are exemplified. These rings may be further substituted. Although there is no particular limitation on the substituent, examples of the substituent include a halogen atom (e.g., chlorine, bromine, iodine or fluorine), a mercapto group, a cyano group, a carboxyl group, a phosphoric acid group, a sulfo group, a hydroxyl group, a carbamoyl group having from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms and more preferably from 2 to 5 carbon atoms (e.g., methylcarbamoyl, ethylcarbamoyl or morpholinocarbonyl), a sulfamoyl group having from 0 to 10 carbon atoms, preferably from 2 to 8 carbon atoms and more preferably from 2 to 5 carbon atoms (e.g., methylsulfamoyl, ethylsulfamoyl or piperidinosulfonyl), a nitro group, an alkoxyl group having from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 8 carbon atoms (e.g., methoxy, ethoxy, 2-methoxy or 2-phenylethoxy), an aryloxy group having from 6 to 20 carbon atoms, preferably from 6 to 12 carbon atoms and more preferably from 6 to 10 carbon atoms (e.g., phenoxy, p-methylphenoxy, p-chlorophenoxy or naphthoxy), an acyl group having form 1 to 20 carbon atoms, preferably from 2 to 12 carbon atoms and more preferably from 2 to 8 carbon atoms (e. g., acetyl, benzoyl or trichloroacetyl), an acyloxy group having form 1 to 20 carbon atoms, preferably from 2 to 12 carbon atoms and more preferably from 2 to 8 carbon atoms (e.g., acetyloxy or benzoyloxy), an acylamino group having form 1 to 20 carbon atoms, preferably from 2 to 12 carbon atoms and more preferably from 2 to 8 carbon atoms (e. g. , acetylamino), a sulfonyl group having form 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 8 carbon atoms (e.g., methanesulfonyl, ethanesulfonyl or benzenesulfonyl), a sulfinyl group having form 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 8 carbon atoms (e.g., methanesulfinyl, ethanesulfinyl or benzenesulfinyl), a sulfonylamino group having form 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 8 carbon atoms (e.g., methanesulfonylamino, ethanesulfonylamino or benzenesulfonylamino), an amino group, a substituted amino group having form 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms and more preferably from 1 to 8 carbon atoms (e.g., methylamino, dimethylamino, benzylamino, anilino or diphenylamino), an ammonium group having form 0 to 15 carbon atoms, preferably from 3 to 10 carbon atoms and more preferably from 3 to 6 carbon atoms (e.g., trimethylammonium or triethylammonium), a hydrazino group having form 0 to 15 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 6 carbon atoms (e.g., trimethylhydrazino), an ureido group having form 1 to 15 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 6 carbon atoms (e. g., ureido or N,N-dimethylureido), an imido group having form 1 to 15 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 6 carbon atoms (e.g., succinimido), an alkylthio group having form 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms and more preferably from 1 to 8 carbon atoms (e.g., methylthio, ethylthio or propylthio), an arylthio group having form 6 to 20 carbon atoms, preferably from 6 to 12 carbon atoms and more preferably from 6 to 10 carbon atoms (e.g., phenylthio, p-methylphenylthio, p-chlorophenylthio, 2-pyridylthio or naphthylthio), an alkoxycarbonyl group having form 2 to 20 carbon atoms, preferably from 2 to 12 carbon atoms and more preferably from 2 to 8 carbon atoms (e. g. , methoxycarbonyl, ethoxycarbonyl or 2-benzyloxycarbonyl), an aryloxycarbonyl group having form 6 to 20 carbon atoms, preferably from 6 to 12 carbon atoms and more preferably from 6 to 10 carbon atoms (e.g., phenoxycarbonyl) an unsubstituted alkyl group having form 1 to 18 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 5 carbon atoms (e.g., methyl, ethyl, propyl or butyl), a substituted alkyl group having form 1 to 18 carbon atoms, preferably from 1 to 10 carbon atoms and more preferably from 1 to 5 carbon atoms (e.g., hydroxymethyl, trifluoromethyl, benzyl, carboxyethyl, ethoxycarbonylmethyl or acetylaminomethyl, wherein an unsaturated hydrocarbon group having form 2 to 18 carbon atoms, preferably from 3 to 10 carbon atoms and more preferably from 3 to 5 carbon atoms (e. g., vinyl, ethynyl, 1-cyclohexenyl, benzylidyne or benzylidene) shall be included in the substituted alkyl group), a substituted or unsubstituted aryl group having form 6 to 20 carbon atoms, preferably from 6 to 15 carbon atoms and more preferably from 6 to 10 carbon atoms (e.g., phenyl, naphthyl, p-carboxyphenyl, p-nitrophenyl, 3,5-dichlorophenyl, p-cyanophenyl, m-fluorophenyl or p-tolyl), and a substituted or unsubstituted heterocyclic group having form 1 to 20 carbon atoms, preferably from 2 to 10 carbon atoms and more preferably from 4 to 6 carbon atoms (e.g., pyridyl, 5-methylpyridyl, thienyl, furyl, morpholino or tetrahydrofurfuryl). They may also have a structure condensed with benzene rings or naphthalene rings. The group of these substituents is hereinafter referred to as substituent group V.
Further, these substituents may be substituted by the substituents hitherto described. As the substituents, preferred are halogen atoms, alkoxyl groups, aryl groups or alkyl groups.
Z1 is preferably a naphtho[2,1-d]oxazole ring, and particularly preferably an unsubstituted naphtho[2,1-d]oxazole ring.
R1, R2, R3, R4, R5 and R6 each represents an alkyl group, an aryl group or a heterocyclic group, which may be further substituted. Specific examples of R1, R3 and R5 include an unsubstituted alkyl group having form 1 to 18 carbon atoms, preferably from 1 to 7 carbon atoms and particularly preferably from 1 to 4 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl, dodecyl or octadecyl); a substituted alkyl group having form 1 to 18 carbon atoms, preferably from 1 to 7 carbon atoms and particularly preferably from 1 to 4 carbon atoms (e.g., alkyl groups substituted by substituent group V described above as the substituents, preferably an aralkyl group (e.g., benzyl or 2-phenylethyl), an unsubstituted hydrocarbon group (e.g., allyl), a hydroxyalkyl group (e.g., 2-hydroxyethyl or 3-hydroxypropyl), a carboxyalkyl group (e.g., 2-carboxyethyl, 3-carboxypropyl, 4-carboxybutyl or carboxymethyl), an alkoxyalkyl group (e.g., 2-methoxyethyl or 2-(2-methoxyethoxy)ethyl), an aryloxyalkyl group (e.g., 2-phenoxyethyl or 2-(1-naphthoxy)ethyl), an alkoxycarbonylalkyl group (e.g., ethoxycarbonylmethyl or 2-benzyloxycarbonylethyl), an aryloxycarbonylalkyl group (e.g. 3-phenoxycarbonylpropyl), an acyloxyalkyl group (e.g., 2-acetyloxyethyl), an acylalkyl group (e.g. , 2-acetylethyl), a carbamoylalkyl group (e.g., 2-morpholinocarbonylethyl), a sulfamoylalkyl group (e.g., N,N-dimethylcarbamoylmethyl), a sulfoalkyl group (e.g., 2-sulfoethyl, 3-sulfopropyl 3-sulfobutyl, 4-sulfobutyl, 2-[3-sulfopropoxy]ethyl, 2-hydroxy-3-sulfopropyl or 3-sulfopropoxyethoxyethyl), a sulfoalkenyl group, a sulfatoalkyl group (e.g., 2-sulfatoethyl, 3-sulfatopropyl or 4-sulfatobutyl), a heterocycle-substituted alkyl group (e.g., 2-(pyrrolidine-2-one-1-yl)ethyl or tetrahydrofurfuryl) and an alkylsulfonylcarbamoylmethyl group (e.g., methanesulfonylcarbamoylmethyl); an unsubstituted aryl group having form 6 to 20 carbon atoms, preferably from 6 to 10 carbon atoms and more preferably from 6 to 8 carbon atoms (e.g., phenyl or 1-naphthyl); a substituted aryl group having form 6 to 20 carbon atoms, preferably from 6 to 10 carbon atoms and more preferably from 6 to 8 carbon atoms (e.g., aryl groups substituted by substituent group V described above as the examples of the substituents, such as p-methoxyphenyl, p-methylphenyl and p-chlorophenyl); an unsubstituted heterocyclic group having form 1 to 20 carbon atoms, preferably from 3 to 10 carbon atoms and more preferably from 4 to 8 carbon atoms (e.g., 2-furyl, 2-thienyl, 2-pyridyl, 3-pyrazolyl, 3-isooxazolyl, 3-isothiazolyl, 2-imidazolyl, 2-oxazolyl, 2-thazolyl, 2-pyridazyl, 2-pyrimidyl, 3-pyrazyl, 2-(1,3,5-triazolyl), 3-(1,2,4-triazolyl) or 5-tetrazolyl); and a substituted heterocyclic group having form 1 to 20 carbon atoms, preferably from 3 to 10 carbon atoms and more preferably from 4 to 8 carbon atoms (e.g., heterocyclic groups substituted by substituent group V described above as the examples of the substituents, such as 5-methyl-2-thienyl or 4-methoxy-2-pyridyl). Examples of substituents for the alkyl groups preferably include a hydroxyl group, a carboxyl group, a sulfo group, a sulfato group, a phosphono group, an alkylsulfonylcarbamoyl group (e.g., methanesulfonylcarbamoyl), an acylcarbamoyl group (e.g., acetylcarbamoyl), an acylsulfamoyl group (e.g., acetylsulfamoyl), an alkylsulfonylsulfamoyl group (e.g., methanesulfonylsulfamoyl), an aryl group, an alkoxyl group and an aryloxy group. More preferred is a sulfo group among these.
R1, R3 and R5 are each preferably an unsubstituted alkyl group having form 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, octyl, decyl, dodecyl or octadecyl), or a sulfoalkyl group (e.g., sulfobutyl or sulfopropyl), and particularly preferably an unsubstituted alkyl group having from 5 t 10 carbon atoms (e.g., n-octyl or n-pentyl).
R2, R4 and R6 are each preferably an unsubstituted alkyl group having form 1 to 18 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, octyl, dodecyl or octadecyl). As a substituted alkyl group, preferred is an aralkyl group (e.g., benzyl or 2-phenylethyl), a hydroxyalkyl group (e.g., 2-hydroxyethyl or 3-hydroxypropyl), a mercaptoalkyl group (e.g., 2-mercaptoethyl), a carboxyalkyl group (e.g., carboxymethyl, 2-carboxyethyl, 3-carboxypropyl, or 4-carboxybutyl), an alkoxyalkyl group (e.g., 2-methoxyethyl, 2-(2-hydroxyethoxy)ethyl or 2-(2-methoxyethoxy)ethyl), an aryloxyalkyl group (e.g., 1-naphthyloxy), a sulfoalkyl group (e.g., 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, 2-(3-sulfopropoxy)ethyl, 2-hydroxy-3-sulfopropyl or 3-sulfopropoxyethoxyethyl), a sulfatoalkyl group (e.g., 3-sulfatopropyl or 4-sulfatobutyl), an arylthioalkyl group (e.g., phenylthioethyl), a heterocycle-substituted alkyl group (e.g., 2-(pyrrolidine-2-one-1-yl) ethyl, tetrahydrofurfuryl or 2-morpholinoethyl), 2-acetoxyethyl, carbomethoxymethyl or 2-methanesulfonylaminoethyl.
R2, R4 and R6 are each more preferably an unsubstituted carboxyalkyl group having 5 or less carbon atoms (e.g., carboxymethyl, carboxyethyl, carboxypropyl or carboxybutyl), and particularly preferably carboxymethyl.
V1, V2, V3, V4, V5, V6, V7, V8, V9 and V10 each represents a hydrogen atom or a substituent. The substituents include substituent group V described above.
Although V1 to V2 are each preferably a hydrogen atom, an alkyl group, a halogen atom, an alkoxyl group or aryl group, particularly preferred is the case that V1 to V7 and V10 are each hydrogen atom and V8 and V9 are each an alkyl group.
L1, L2, L3, L4 , L5, L6, L7, L8, L9, L10, L11 and L12 each represents an unsubstituted methine group or a substituted methine group (e.g., a methine group substituted by an unsubstituted or substituted alkyl group(e.g.,methyl, ethyl or 2-carboxyethyl), an unsubstituted or substituted aryl group (e.g., phenyl or 2-carboxyphenyl), a heterocyclic group (e.g., thienyl or barbituric acid group), a halogen atom (chlorine or bromine), an alkoxyl group (e.g., methoxyorethoxy), an amino group (e.g., N,N-diphenylamino, N-methyl-N-phenylamino or N-methylpiperazino) or an alkylthio group (e.g., methylthio or ethylthio)), and may form a ring with another methine group or with an auxochrome (for example, L1 can form a ring with R1).
L3, L7 and L11 are each preferably an unsubstituted methine group or a methine group substituted by an alkyl group (e.g., methyl), an alkoxyl group (e.g., methoxy), an amino group (e.g., N-diphenyl amino) or a halogen atom (e.g., chlorine), of substituted methine groups. Particularly preferred is a methine group substituted by methyl.
L1, L2, L4, L5, L6, L8, L9, L10 and L12 are each preferably an unsubstituted methine group.
As a combination of L1, L2, L3 and L4, particularly preferred is the case that L1, L2 and L4 are each an unsubstituted methine group and L3 is a methine group substituted by methyl.
As a combination of L5, L6, L7 and L8, particularly preferred is the case that L5, L6 and L8 are each an unsubstituted methine group and L7 is a methine group substituted by methyl.
As a combination of L9, L10, L11 and L12, particularly preferred is the case that L9, L10 and L12 are each an unsubstituted methine group and L11 is a methine group substituted by methyl.
(M1)m1, (M2)m2 and (M3)m3 are contained in the formulas for indicating the presence or absence of a cation or an anion when it is necessary for neutralizing an ion charge of a dye. It depends on an auxochrome or a substituent thereof whether a given dye is a cation or an anion, or whether it has a net ion charge or not. Examples of the typical cation include a hydrogen ion, an inorganic ammonium ion, an organic ammonium ion (e.g., a tetraalkylammonium ion, a pyridinium ion, a triethylamine salt or a 1,8-diazabicyclo[5,4,0]-7-undecene salt), an alkali metal ion (e.g., a sodium ion or a potassium ion), or an alkaline earth metal ion (e.g., a calcium ion). On the other hand, the anion may be specifically either an inorganic anion oranorganic anion, and examples thereof include, for example, a halogen anion (e.g., a fluoride ion, a chloride ion, a bromide ion or an iodide ion), a substituted arylsulfonic acid ion (e.g., p-toluenesulfonic acid ion or p-chlorobenzenesulfonic acid ion), an aryldisulfonic acid ion (e.g., a 1,3-benzenedisulfonic acid ion, a 1,5-naphthalenedisulfonic acid ion or a 2,6-naphthalenedisulfonic acid ion), an alkylsulfuric acid ion (e.g., methylsulfuric acid ion), a sulfuric acid ion, a thiocyanic acid ion, a perchloric acid ion, a tetrafluoroboric acid ion, a picric acid ion, an acetic acid ion and a trifluoromethanesulfonic acid ion. As a charge balancing counter ion, an ionic polymer or another dye having a reverse charge to a dye may be used, or a metal complex ion (e.g., bisbenzene-1,2-dithiolato nickel (III)) is available. Preferred are a hydrogen ion, an ammonium ion (e.g., a triethylamine salt or a 1,8-diazabicyclo-[5,4,0]-7-undecene salt) and an alkali metal ion (e.g., a sodium ion or a potassium ion), and particularly preferred are a hydrogen ion, a sodium ion, a potassium ion and a triethylamine salt.
Typical examples of the merocyanine dyes represented by formula (I) include but are not limited to the following:
Typical examples of the merocyanine dyes represented by formula (III) include but are not limited to the following:
The merocyanine dyes represented by formulas (I) to (III) which are used in the present invention can be synthesized based on methods described in the following literatures:
a) F. M. Hamer, Heterocyclic Compoundsxe2x80x94Cyanine dyes and related compounds-, John Wiley and Sons, New York, London, 1964;
b) D. M. Sturmer, Heterocyclic Compoundsxe2x80x94Special topics in heterocyclic chemistry-, chapter 8, section 4, pages 482 to 515, John Wiley and Sons, New York, London, 1977; and
c) Rodds Chemistry of Carbon Compounds, (2nd ed., vol. IV, part B, 1977), chapter 15, pages 369 to 422; (2nd ed., vol. IV, part B, 1985), chapter 15, pages 267 to 296, Elsevier Science Publishing Company Inc., New York.
A method for synthesizing themerocyanine dyes represented by formulas (I) and (II) will be described below by reference to a specific example.
2-Methylnaphtho[2,1-d]oxazole (2.4 g) and 3.5 ml of n-octyl iodide were stirred at 160xc2x0 C. for 6 hours, and then, 7 ml of acetic anhydride and 7 g of 1,1,3,3-tetraethoxy-2-methylpropane were added thereto, followed by stirring at 100xc2x0 C. for 1 hour. The mixture was allowed to cool to room temperature, and ethyl acetate and hexane were added thereto. Then, 2.6 g of a solid 2-(4-ethoxy-3-methyl-1,3-butadienyl)-3-octyl-naphtho[2,1-d]oxazolium iodide salt thus produced was corrected by filtration. This solid (2.5 g) and 0.96 g of 3-carboxymethylrhodanine were dissolved in 10 ml of acetonitrile, and 2.1 ml of triethylamine was added thereto. After the reaction solution was stirred at room temperature for 1 hour, 1 ml of acetic acid was added thereto, and the resulting crude crystals were corrected by filtration. These crude crystals were recrystallized from methanol to obtain 2.1 g of compound 4.
xcex max(MeOH)=591 nm, ∈=1.04xc3x97105 (MeOH), melting point: 258 to 260xc2x0 C.
Other compounds of the present invention can also be synthesized by methods similar to the above-described Synthesis Example.
The merocyanine dyes represented by formulas (I) and (II) of the present invention may be used in a desired amount, providing a match to characteristics such as sensitivity and fog. However, they are used preferably in an amount of 10xe2x88x926 mol to 1 mol, and more preferably in an amount of 10xe2x88x924 mol to 10xe2x88x921 mol, per mol of silver halide of a light-sensitive layer.
As the sensitizing dyes in the present invention, dyes having structures other than the structures represented by formulas (I) and (II) may be used in combination with the dyes represented by formulas (I) and (II). Particularly preferred dyes which can be used in combination are the merocyanine dyes represented by formula (III). Further, a plurality of dyes can also be used as a mixture to obtain a desired spectral sensitization spectrum.
The mixing ratio of the merocyanine dyes represented by formulas (I) and (II) to the merocyanine dyes represented by formula (III) may be any. However, it is preferably within the range of 1:10 to 10:1, and particularly preferably within the range of 1:2 to 2:1, in the molar ratio.
These sensitizing dyes may be used alone or as a combination of two or more of them. Combinations of the sensitizing dyes are of ten used particularly for supersensitization. Emulsions may contain dyes having no spectral sensitizing function for themselves, or substances which do not substantially absorb visible light and exhibit supersensitization, together with the sensitizing dyes. The useful sensitizing dyes, the combinations of the dyes showing supersensitization, and the substances exhibiting supersensitization are described in Research Disclosure, 176, 17643, p.23, item IV-J, (December, 1978) or JP-B-49-25500 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d), JP-B-43-4933, JP-A-59-19032 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and JP-A-59-192242.
When the sensitizing dyes are added to the silver halide emulsions, they may be directly dispersed in the emulsions, or may be dissolved in single or mixed solvents of water, methanol, ethanol, propanol, acetone, methyl cellosolve, 2,2,3,3-tetrafluoropropanol, 2,2,2-trifluoroethanol, 3-methoxy-1-propanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol and N,N-dimethylformamide to add them to the emulsions as solutions.
Further, methods which can be used in the present invention include a method of dissolving a dye in a volatile organic solvent, dispersing the resulting solution into water or a hydrophilic colloid, and adding the resulting dispersion to an emulsion, as described in U.S. Pat. No. 3,469,987; a method of dissolving a dye in an acid, and adding the resulting solution to an emulsion, or dissolving a dye in water in the presence of an acid or a base, and adding the resulting aqueous solution to an emulsion, as described in JP-B-44-23389, JP-B-44-27555 and JP-B-57-22091; a method of dissolving or dispersing a dye into water in the presence of a surfactant, and adding the resulting aqueous solution or colloidal dispersion to an emulsion, as described in U.S. Pat. Nos. 3,822,135 and 4,006,025; a method of directly dispersing a dye into a hydrophilic colloid, and adding the resulting dispersion to an emulsion, as described in JP-A-53-102733 and JP-A-58-105141; and a method of dissolving a dye by the use of a red-shifting compound, and adding the resulting solution to an emulsion, as described in JP-A-51-74624. Further, ultrasonic waves can also be applied to the solution.
The sensitizing dyes used in the present invention may be added at any stages of the preparation of the silver halide emulsions which have hitherto been accepted to be useful. For example, they may be added at a silver halide grain formation stage and/or before desalting, during a silver-removing stage and/or from after desalting to before the start of chemical ripening, as described in U.S. Pat. Nos. 2,735,766, 3,628,960, 4,183,756 and 4,225,666, JP-A-58-184142 and JP-A-60-196749, or at any time and stage before the coating of emulsions, such as immediately before or during chemical ripening, or from after chemical ripening to the coating of the emulsions, as described in JP-A-58-113920. Furthermore, as disclosed in U.S. Pat. No. 4,225,666 and JP-A-58-7629, the same compound maybe singly added, or in combination with a compound having a foreign structure, divided, for example, into during a grain formation stage and during or after chemical ripening, or before or during chemical ripening and after chemical ripening. The kinds of compounds added in parts and combinations thereof may be changed.
The organic silver salt which can be used in the present invention is relatively stable to light, and is a silver salt forming a silver image when heated to a temperature of 80xc2x0 C. or more in the presence of an exposed photocatalyst (such as a latent image of a light-sensitive silver halide) and a reducing agent. The organic silver salt may be any organic substance containing a source which can reduce a silver ion. Such light-insensitive organic silver salts are described in JP-A-10-62899, paragraph numbers 0048 to 0049, EP-A-0803764, page 18, line 24 to page 19, line 37, and EP-A-0962812. Silver salts of organic acids, particularly silver salts of long-chain aliphatic carboxylic acids (each having from 10 to 30 carbon atoms, and preferably from 15 to 28 carbon atoms), are preferred. Preferred examples of the organic silver salts include silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, and mixtures thereof. In the present invention, of these organic silver salts, an organic acid silver salt having a silver behenate content of 75 mol % or more is preferably used.
There is no particular limitation on the form of the organic silver salts which can be used in the present invention, and they may be acicular, rod-like, tabular or scaly.
In the present invention, scaly organic silver salts are preferred. In this specification, the term xe2x80x9cscaly organic silver saltxe2x80x9d is defined as follows. The organic acid silver salt is observed under an electron microscope, and the form of an organic acid silver salt particle is approximated to a rectangular parallelepiped. When the sides of this rectangular parallelepiped are taken as a, b and c from the shortest one (c may be equal to b), x is calculated by the following equation using shorter numerical values a and b:
xe2x80x83X=b/a
x is determined in this manner for about 200 particles, and the average value thereof is taken as x (average). The particles satisfying the relationship of x (average)xe2x89xa71.5 are defined as scaly particles. The relationship is preferably 30xe2x89xa7x (average)xe2x89xa71.5, and more preferably 20xe2x89xa7x (average)xe2x89xa72.0. By the way, when 1xe2x89xa6x (average) less than 1.5 is satisfied, the particles are defined as acicular particles.
In the scaly particle, a can be considered as the thickness of a tabular particle in which a plane having sides b and c is a main plane. The average of a is preferably from 0.01 xcexcm to 0.23 xcexcm, and more preferably from 0.1 xcexcm to 0.20 xcexcm. The average of c/b is preferably from 1 to 6, more preferably from 1.05 to 4, still more preferably from 1.1 to 3, and particularly preferably from 1.1 to 2.
It is preferred that the organic silver salt has monodisperse particle size distribution. The term xe2x80x9cmonodispersexe2x80x9d means that the percentage of a value of the standard deviation of each length of the short and long axes divided by each the short and long axes is preferably 100% or less, more preferably 80% or less, and still more preferably 50% or less. The form of the organic silver salt can be measured by an image of an organic silver salt dispersion observed under a transmission electron microscope. As another method for measuring the monodispersibility, there is a method of determining the standard deviation of volume weighted average diameters of the organic silver salt. The percentage (the coefficient of variation) of values divided by volume weighted average diameters is preferably 100% or less, more preferably 80% or less, and still more preferably 50% or less. This can be determined, for example, from particle sizes (volume weighted average diameters) determined by irradiating laser light to the organic silver salt dispersed in a solution and determining the auto correlation function to changes in fluctuation of its scattered light with time.
To methods for producing and dispersing the organic acid silver salts used in the present invention, well-known methods can be applied. For example, JP-A-10-62899, EP-A-0803763 and EP-A-0962812 described above can be referred to.
In the present invention, the coexistence of a light-sensitive silver salt at dispersing the organic silver salt results in an increase in fog and extreme decrease of sensitivity. Accordingly, it is more preferred that a light-sensitive silver salt is not substantially contained at dispersing the organic silver salt. In the present invention, the amount of the light-sensitive silver salt contained in an aqueous dispersion is preferably 0.1 mol % or less per mol of organic acid silver salt in the dispersion, and the light-sensitive silver salt is not positively added.
In the present invention, it is possible to produce the light-sensitive material by mixing the aqueous dispersion of the organic silver salt with the aqueous dispersion of the light-sensitive silver salt. The mixing ratio of the organic silver salt to the light-sensitive silver salt can be selected depending on the purpose. However, the ratio of the light-sensitive silver salt to the organic silver salt is preferably within the range of 1 mol % to 30 mol %, more preferably within the range of 3 mol % to 20 mol %, and particularly preferably within the range of 5 mol % to 15 mol %. In mixing, it is preferably used for adjusting the photographic characteristics that two or more kinds of aqueous dispersions of organic silver salts are mixed with two or more kinds of aqueous dispersions of light-sensitive silver salts.
In the present invention, the organic silver salts can be used in a desired amount. However, they are used preferably in an amount of 0.1 g/m2 to 5 g/m2, and more preferably in an amount of 1 g/m2 to 3 g/m2, in terms of silver.
It is preferred that the photothermographic materials of the present invention contain reducing agents for the organic silver salts. The reducing agents for the organic silver salts maybe any substances for reducing a silver ion to metallic silver (preferably organic substances). Such reducing agents are described in JP-A-11-65021, paragraph numbers 0043 to 0045, and EP-A-0803764, page 7, line 34 to page 18, line 12. In the present invention, bisphenol reducing agents (e.g., 1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane), 2,2xe2x80x2-methylenebis-(4-methyl-6-tert-butylphenol) and 2,2xe2x80x2-ethylenebis-(4-methyl-6-tert-butylphenol) are particularly preferred. The amount of the reducing agents added is preferably from 0.01 g/m2 to 5.0 g/m2, and more preferably from 0.1 g/m2 to 3.0 g/m2. They are contained preferably in an amount of 5 mol % to 50 mol %, and more preferably in an amount of 10 mol % to 40 mol %, per mol of silver of a face having an image formation layer. The reducing agents are preferably contained in the image formation layers.
The reducing agents may be added to coating solutions by any methods such as solution methods, emulsified dispersion methods and fine solid particle dispersion methods, thereby allowing them to be contained in the light-sensitive materials.
The well-known emulsified dispersion methods include a method of dissolving the reducing agents using oils such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate, and diethylphthalate or co-solvents (i.e., auxiliary solvents) such as ethyl acetate and cyclohexanone, and mechanically preparing emulsified dispersions.
Further, the fine solid particle dispersion methods include a method of dispersing reducing agent powder in appropriate solvents such as water by a ball mill, a colloid mill, a vibrating ball mill, a sand mill, a jet mill or a roller mill, or by a supersonic wave to prepare solid dispersions. In that case, protective colloids (e.g., polyvinyl alcohol) and surfactants (e.g., anionic surfactants such as sodium triisopropylnaphthalenesulfonate (a mixture of three isomers different in substitution positions of isopropyl groups) may be used. The aqueous dispersion may contain preservatives (e.g., benzoisothiazolinone sodium salt).
In the photothermographic materials of invention, phenol derivatives represented by formula (A) described in JP-A-267222/2000 are preferably used as development accelerators.
There is no particular limitation on the composition of the light-sensitive silver halides used in the present invention, and silver chloride, silver chlorobromide, silver bromide, silver iodobromide and silver iodochlorobromide can be used. The distribution of the halogen composition in the grain may be uniform, or the halogen composition may vary stepwise or continuously. Further, silver halide grains having the core/shell structure can be preferably used. Double to five fold structure type core/shell grains can be preferably used, and double to fourfold structure type core/shell grains can be more preferably used. Furthermore, a process of localizing silver bromide on the surfaces of silver chloride or silver chlorobromide grains can also preferably used.
Methods for forming the light-sensitive silver halides are well-known in the art. For example, methods described in Research Disclosure, vol. 17029 (June, 1978) and U.S. Pat. No. 3,700,458 can be used. Specifically, a method of adding a silver supplying compound and a halogen supplying compound to a gelatin solution or another polymer solution to prepare light-sensitive silver halide grains (silver halide emulsion), and then, mixing the resulting silver halide grains with an organic silver salt is used.
Also, methods described in JP-A-11-119374(paragraph numbers 0217-0224), JP-A-11-352627 and JP-A-347335/2000 can be preferably used.
For inhibiting white turbidity after image formation, it is preferred that the grain size of the light-sensitive silver halide is small. Specifically, the grain size is preferably 0.20 xcexcm or less, more preferably from 0.01 xcexcm to 0.15 xcexcm, and still more preferably from 0.02 xcexcm to 0.12 xcexcm. The term xe2x80x9cgrain sizexe2x80x9d as used herein means the diameter of a sphere having the same volume as that of the silver halide grain, when the silver halide grain is a normal (i.e., regular) crystal such as a cube or octahedron, and is not a normal crystal, such as a spherical or rod-like grain. When the silver halide grain is a tabular grain, the grains size means the diameter of a circle image having the same area as a projected area of a main surface.
The form of the silver halide grains may be cubic, octahedral, tabular, spherical, rod-like or pebble-like. In the present invention, however, cubic grains are particularly preferred. Silver halide grain shaving rounded corners can also be preferably used. There is no particular limitation on the surface index (mirror index) of outer surfaces of the light-sensitive silver halide grains. However, it is preferred that the ratio of the [100] face having high spectral sensitization efficiency when a spectral sensitizing dye is adsorbed thereby is high. The ratio is preferably 50% or more, more preferably 65% or more, and most preferably 80% or more. The ratio of the mirror index [100] face can be determined by a method described in T. Tani, J., Imaging Sci., 29, 165 (1985), utilizing adsorption dependency of the [111] face and the [100] face in adsorption of a sensitizing dye.
The light-sensitive silver halide grains of the present invention contain metals or metal complexes of groups VIII to X in the periodic table (showing groups I to XVIII). The metals or central metals of the metal complexes of groups VIII to X in the periodic table are rhodium, ruthenium and iridium. These metal complexes may be used either alone or as a combination of two or more of complexes comprising the same kind or foreign kinds of metals. The content thereof is preferably from 1xc3x9710xe2x88x929 mol to 1xc3x9710xe2x88x923 mol per mol of silver. These heavy metals, metal complexes and methods for adding them are described in JP-A-7-225449, JP-A-11-65021, paragraph numbers 0018 to 0024, and JP-A-11-119374, paragraph numbers 0227 to 0240.
Of these, the iridium compounds are preferably contained in the silver halide grains in the present invention. Examples of the iridium compounds include, for example, hexachloroiridium, hexaammineiridium, trioxalatoiridium and hexacyanoiridium. These iridium compounds are used by dissolving them in water or appropriate solvents. In order to stabilize the solution of the iridium compound, a method ordinarily frequently used, that is to say, a method of adding an aqueous solution of a hydrogen halide (e.g., hydrochloric acid, hydrobromic acid or hydrofluoric acid) or an alkali halide (e.g., KCl, NaCl, KBr or NaBr), which is generally frequently used, can be used. Instead of use of the water-soluble iridium, it is also possible to add and dissolve other silver halide grains previously doped with iridium in preparing the silver halide. These iridium compounds are added preferably in an amount ranging from 1xc3x9710xe2x88x928 mol to 1xc3x9710xe2x88x923 mol, and more preferably in an amount ranging from 1xc3x9710xe2x88x927 mol to 5xc3x9710xe2x88x924 mol, per mol of silver halide.
Further, metal atoms which can be contained in the silver halide grains used in the present invention (e.g., [Fe(CN)6]4xe2x88x92), desalting methods and chemical sensitizing methods are described in JP-A-11-84574, paragraph numbers 0046 to 0050, JP-A-11-65021, paragraph numbers 0025 to 0031, and JP-A-11-119374, paragraph number 0242 to 0250.
As gelatins contained in the light-sensitive silver halide emulsions (silver halide emulsions containing the light-sensitive silver halides) used in the present invention, there can be used various kinds of gelatins. In order to keep good the dispersing state of the light-sensitive silver halide emulsions inorganic silver salt-containing coating solutions, it is preferred that low molecular weight gelatins having a molecular weight of 500 to 60,000 are used. Although these low molecular weight gelatins may be used at forming the grains, or at dispersing the grains after desalting, they are preferably used at dispersing the grains after desalting.
As the sensitizing dyes applicable to the present invention, there can be selected sensitizing dyes which can spectrally sensitize the silver halide grains in adesired wavelength region when adsorbed by the silver halide grains, and which have spectral sensitivity suitable for the spectral characteristics of an exposure light source. The sensitizing dyes and methods for adding them are described in JP-A-11-65021, paragraph numbers 0103 to 0109, JP-A-10-186572 (compounds represented by formula (II)), JP-A-11-119374 (dyes represented by formula (I) and paragraph number 0106), U.S. Pat. Nos. 5,510,236 and 3,871,887 (dyes described in Example 5), JP-A-2-96131, JP-A-59-48753 (dyes described therein) and EP-A-0803764, page 19, line 38 to page 20, line 35. These sensitizing dyes may be used either alone or as a combination of two or more of them. In the present invention, the sensitizing dyes are added to the silver halide emulsions preferably from after desalting to coating, and more preferably from after desalting to before the start of chemical ripening.
In the present invention, the sensitizing dyes may be used in a desired amount depending on performances such as sensitivity and fog. However, they are used preferably in an amount of 10xe2x88x926 mol to 1 mol, and more preferably in an amount of 10xe2x88x924 mol to 10xe2x88x921 mol, per mol of silver halide of the light-sensitive layer.
In the present invention, for improving spectral sensitization efficiency, supersensitizing agents can be used. The supersensitizing agents used in the present invention include compounds described in EP-A-587,338, U.S. Pat. Nos. 3,877,943 and 4,873,184, JP-A-5-341432, JP-A-11-109547 and JP-A-10-111542.
It is preferred that the light-sensitive silver halide grains contained in the silver halide emulsions in the present invention are chemically sensitized by sulfur sensitization, selenium sensitization or tellurium sensitization. As compounds preferably used for sulfur sensitization, selenium sensitization and tellurium sensitization, there can be used well-known compounds, for example, compounds described in JP-A-7-128768. In particular, tellurium sensitizers are preferably used in the present invention, and more preferred are compounds described in literatures described in JP-A-11-65021, paragraph number 0030, and compounds represented by formulas (II), (III) and (IV) in JP-A-5-313284.
In the present invention, chemical sensitization is possible at any time, such as (1) before spectral sensitization, (2) concurrently with spectral sensitization, (3) after spectral sensitization or (4) immediately before coating, after desalting, as long as it is conducted after grain formation and before coating. In particular, chemical sensitization is preferably conducted after spectral sensitization.
The amount of sulfur, selenium and tellurium sensitizers used in the present invention is from 1xc3x9710xe2x88x928 mol to 1xc3x9710xe2x88x922 mol, and preferably from about 1xc3x9710xe2x88x927 mol to about 1xc3x9710xe2x88x923 mol, per mol of silver halide, although it varies depending on silver halide grains used and chemical ripening conditions. There is no particular limitation on the conditions of chemical sensitization in the present invention. However, the pH is from 5 to 8, the pAg is from 6 to 11, and the temperature is from about 40xc2x0 C. to about 95xc2x0 C.
Thiosulfonic acid compounds may be added to the silver halide emulsions used in the present invention by a method shown in EP-A-293,917.
The light-sensitive silver halide emulsions in the light-sensitive materials used in the present invention may be used either alone or as a combination of two or more of them (for example, emulsions different in mean grain size, emulsions different in halogen composition, emulsions different in crystal habit, and emulsions different in the conditions of chemical sensitization). The use of plural kinds of light-sensitive silver halides different in sensitivity allows the gradation to be controlled. Techniques relating to these are described in JP-A-57-119341, JP-A-53-106125, JP-A-47-3929, JP-A-48-55730, JP-A-46-5187, JP-A-50-73627 and JP-A-57-150841. As to the difference in sensitivity, a difference of 0.21 logE or more is preferably given between the respective emulsions.
The amount of the light-sensitive silver halides added is preferably from 0.03 g/m2 to 0.6 g/m2, more preferably from 0.05 g/m2 to 0.4 g/m2, and most preferably from 0.1 g/m2 to 0.4 g/m2, in terms of the amount of silver coated per m2 of light-sensitive material. It is preferably from 0.01 mol to 0.5 mol, and more preferably from 0.02 mol to 0.3 mol, per mol of organic silver salt.
As processes for mixing the light-sensitive silver halides and the organic silver salts separately prepared and mixing conditions thereof, there are a method of mixing the separately prepared silver halide grains and organic silver salt with each other in a high-speed stirrer, a ball mill, a sand mill, a colloid mill, a vibrating mill or a homogenizer, and a method of mixing the prepared light-sensitive silver halide at any timing during preparation of the organic silver salt to prepare the organic silver salt. However, there is no particular limitation thereon, as long as the effects of the present invention are sufficiently manifested. Further, in mixing, it is a preferred method for adjustment of photographic characteristics that two or more kinds of aqueous dispersions of the organic silver salts are mixed with two or more kinds of aqueous dispersions of the light-sensitive silver salts.
The silver halides used in the present invention are preferably added to the coating solutions for image forming layers from 180 minutes before coating to immediately before coating, preferably from 60 minutes before coating to 10 seconds before coating. However, there is no particular limitation on the mixing process and the mixing conditions, as long as the effects of the present invention are sufficiently manifested. Specific examples of the mixing processes include a mixing process using a tank designed so that the average residence time calculated from the flow rate of the solution added and the amount of the solution supplied to a coater becomes a desired time, and a process using static mixers described in N. Harnby, M. F. Edwards and A. W. Nienow, translated by Koji Takahashi, Liquid Mixing Techniques, chapter 8, published by Nikkan Kogyo Shinbunsha (1989).
Binders for the organic silver salt-containing layers may be any polymers, and suitable binders are transparent or translucent and generally colorless. They are natural and synthetic resins (polymers and copolymers) and other film forming media, and examples thereof include gelatin, gum arabic, poly (vinyl alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butylate, poly(vinylpyrrolidone), casein, starch, poly(acrylic acid), poly(methyl methacrylate), poly(vinyl chloride), poly(methacrylic acid), styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, poly(vinyl acetal) polymers (e.g., poly (vinyl formal) and poly (vinyl butyral)), polyesters polyurethanes, phenoxy resins, poly(vinylidene chloride), polyepoxides, polycarbonates, poly(vinyl acetate), cellulose esters and polyamides. The binders may be formed from aqueous solutions, organic solvent solutions or emulsions by coating.
In the present invention, it is preferred that the organic silver salt-containing layer is formed by applying a coating solution in which 30% by weight or more of a solvent is water, followed by drying, and further it is preferred that the binder of the organic silver salt-containing layer is soluble or dispersible in an aqueous solvent (water solvent) and particularly is composed of a polymer latex having an equilibrium moisture content of 2% by weight or less at 25xc2x0 C., 60% RH. The most preferred form is one prepared so as to give an ionic conductivity of 2.5 mS/cm or less, and as the methods, a method of purifying the polymer with a separation functional membrane after synthesis thereof are exemplified.
The term xe2x80x9can aqueous solvent in which the polymer is soluble or dispersiblexe2x80x9d as used herein means water or a mixture of water and 70% by weight or less of a water-soluble or aqueous-miscible organic solvent. Examples of the aqueous-miscible organic solvents include, for example, alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol, cellosolve derivatives such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, ethyl acetate and dimethylformamide.
When the polymer is not dissolved thermodynamically to exist in a so-called dispersion state, the term xe2x80x9caqueous solventxe2x80x9d is also used herein.
The term xe2x80x9cequilibrium moisture content at 25xc2x0 C., 60% RHxe2x80x9d as used herein can be expressed using the weight W1 of a polymer attaining equilibrium with moisture in the atmosphere of 25xc2x0 C. and 60% RH and the weight W0 of the polymer in the absolute dry condition at 25xc2x0 C. as follows:
Equilibrium Moisture Content at 25xc2x0 C., 60% RH=[(W1xe2x88x92W0)/W0]xc3x97100 (% by weight)
For the definition of the moisture content and the measuring method thereof, reference can be made to Polymer Engineering Course, 14, xe2x80x9cTest Methods of Polymer Materialsxe2x80x9d (edited by Kobunshi Gakkai, Chijin Shokan).
The equilibrium moisture content of the binder polymers of the present invention at 25xc2x0 C., 60% RH is preferably 2% by weight or less, more preferably from 0.01% to 1.5% by weight, and still more preferably from 0.02% to 1% by weight.
In the present invention, polymers dispersible in the aqueous solvents are particularly preferred. Examples of the dispersion states include latexes in which fine particles of water-insoluble hydrophobic polymers are dispersed, and dispersions of polymer molecules dispersed in a molecular state or forming micelles, both of which are preferred. The mean particle size of the dispersed particles is from about 1 nm to about 50,000 nm, and more preferably from about 5 nm to about 1,000 nm. There is no particular limitation on the particle size distribution of the dispersed particles. The particles may be either ones having a wide particle size distribution or ones having a monodisperse particle size distribution.
In the present invention, preferred examples of the polymers dispersible in the aqueous solvents include hydrophobic polymers such as acrylic resins, polyester resins, rubber resins (e.g., SBR resins), polyurethane resins, vinyl chloride resins, vinyl acetate resins, vinylidene chloride resins and polyolefin resins. The polymer may be a straight chain polymer, a branched polymer or a crosslinked polymer. Further, the polymer may be either a so-called homopolymer in which a single monomer is polymerized, or a copolymer in which two or more kinds of monomers are polymerized. The copolymer may be either a random copolymer or a block copolymer. The number average molecular weight of the polymer is preferably from 5,000 to 1,000,000, and more preferably from about 10,000 to about 200,000. Too low a molecular weight unfavorably results in insufficient mechanical strength of the emulsion layer, whereas too high a molecular weight causes poor film forming properties.
Preferred examples of the polymer latexes include the following, wherein the polymers are represented by raw material monomers, the numerals in parentheses are percentages by weight, and the molecular weight is the number average molecular weight.
P-1: Latex of -MMA(70)-EA(27)-MAA(3)-(molecular weight: 37,000);
P-2: Latex of -MMA(70)-2EHA(20)-St(5)-AA(5)-(molecular weight: 40,000);
P-3: Latex of -St(50)-Bu(47)-MAA(3)-(molecular weight: 45,000);
P-4: Latex of -St(68)-Bu(29)-AA(3)-(molecular weight: 60,000);
P-5: Latex of -St(70)-Bu(27)-IA(3)-(molecular weight: 120,000)
P-6: Latex of -St(75)-Bu(24)-AA(1)-(molecular weight: 108,000);
P-7: Latex of -St(60)-Bu(35)-DVB(3)-MAA(2)-(molecular weight: 150,000);
P-8: Latex of -St(70)-Bu(25)-DVB(2)-AA(3)-(molecular weight: 280,000);
P-9: Latex of -VC(50)-MMA(20)-EA(20)-AN(5)-AA(5)-(molecular weight: 80,000);
P-10: Latex of -VDC(85)-MMA(5)-EA(5)-MAA(5)-(molecular weight: 67,000);
P-11: Latex of -Et(90)-MMA(10)-(molecular weight: 12,000);
P-12: Latex of -St(70)-2EHA(27)-AA(3) (molecular weight: 130,000); and
P-13: Latex of -MMA(63)-EA(35)-AA(2) (molecular weight: 33,000).
Abbreviations used in the above-described structures indicate the following monomers:
MMA; Methyl methacrylate, EA; Ethyl acrylate, MAA; Methacrylic acid, 2EHA; 2-Ethylhexyl acrylate, St; Styrene, Bu; Butadiene, AA; Acrylic acid, DVB; Divinylbenzene, VC; Vinyl chloride, AN; Acrylonitrile, VDC; Vinylidene chloride, Et: Ethylene and IA; Itaconic acid
The polymers described above are commercially available, and the following polymers can be utilized. Examples of the acrylic resins include Sebian A-4635, 46583 and 4601 (the above products are manufactured by Daicel Chemical Industries, Ltd.) and Nipol Lx 811, 814, 821, 820 and 857 (the above products are manufactured by Nippon Zeon Co., Ltd), examples of the polyester resins include FINETEXES 650, 611, 675 and 850 (the above products are manufactured by Dainippon Ink and Chemicals, Inc.), and WD-size and WMS (the above products are manufactured by Eastman Chemical Co.), examples of the polyurethane resins include HYDRAN AP 10, 20, 30 and 40 (the above products are manufactured by Dainippon Ink and Chemicals, Inc.), examples of the rubber resins include LACSTAR 7310K, 3307B, 4700H and 7132C (the above products are manufactured by Dainippon Ink and Chemicals, Inc.) and Nipol Lx 416, 410, 438C and 2507 (the above products are manufactured by Nippon Zeon Co., Ltd.), examples of the vinyl chloride resins include G351 and G576 (the above products are manufactured by Nippon Zeon Co., Ltd.), examples of the vinylidene chloride resins include L502 and L513 (the above products are manufactured by Asahi Chemical Industry Co., Ltd.), and examples of the polyolefin resins include Chemipearl S120 and SA100 (the above products are manufactured by Mitsui Petrochemical Industries, Ltd.).
These polymer latexes may be used either alone or as a mixture of two or more of them as required.
As the polymer latexes used in the present invention, styrene-butadiene copolymer latexes are particularly preferred. In the styrene-butadiene copolymer latex, the weight ratio of styrene monomer units to butadiene monomer units is preferably from 40:60 to 95:5. Further, the ratio of the styrene monomer units and the butadiene monomer units to the copolymer is preferably from 60% to 99% by weight. The preferred molecular weight range is the same as described above.
The styrene-butadiene copolymer latexes which can be preferably used in the present invention include P-3 to P-8 described above and commercially available LACSTAR-3307B, 7132C and Nipol Lx416.
The organic silver salt-containing layer of the light-sensitive material of the present invention may further contain a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose or carboxymethyl cellulose. The amount of the hydrophilic polymer added is preferably 30% by weight or less, and more preferably 20% by weight or less, base on the total binder of the organic silver salt-containing layer.
The organic silver salt-containing layer (that is to say, the image formation layer) of the present invention is preferably formed using the polymer latex, and as the amount of binder contained in the organic silver salt-containing layer, the weight ratio of total binder/silver halide is preferably from 1/10 to 10/1, and more preferably from 1/5 to 4/1.
Further, such an organic silver salt-containing layer is also usually a light-sensitive layer (emulsion layer) containing the light-sensitive silver halide that is the light-sensitive silver salt. In such a case, the weight ratio of total binder/silver halide is preferably from 400 to 5, and more preferably from 200 to 10.
The total binder amount of the image formation layer of the present invention is preferably from 0.2 g/m2 to 30 g/m2, and more preferably from 1 g/m2 to 15 g/m2. The image formation layer of the present invention may contain a crosslinking agent for crosslinking and a surfactant for improving coating properties.
In the present invention, the solvent (both the solvent and the dispersing medium are referred to as the solvent herein for brevity) for a coating solution for the organic silver salt-containing layer of the light-sensitive material is an aqueous solvent containing water in an amount of 30% by weight or more. As components other than water, any water-miscible organic solvents such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide and ethyl acetate may be used. The water content of the solvents of the coating solutions is preferably 50% by weight or more, and more preferably 70% by weight or more. Preferred examples of solvent compositions include water/methyl alcohol=90/10, water/methyl alcohol=70/30, water/methyl alcohol/dimethylformamide=80/15/5, water/methyl alcohol/ethyl cellosolve=85/10/5 and water/methyl alcohol/isopropyl alcohol=85/10/5 (wherein the numeral values are percentages by weight), as well as water.
Antifoggants, stabilizers and stabilizer precursors which can be used in the present invention include ones described in patents described in JP-A-10-62899, paragraph number 0070 and EP-A-0803764, page 20, line 57 to page 21, line 7. Further, antifoggants preferably used in the present invention are organic halides, which include ones disclosed in patents described in JP-A-11-65021, paragraph numbers 0111 to 0112. In particular, organic halogen compounds represented by formula (P) of JP-A-284399/2000 and organic polyhalogen compounds represented by formula (II) of JP-A-10-339934 (specifically, tribromomethylnaphthylsulfone, tribromomethylphenylsulfone and tribromomethyl(4-(2,4,6-trimethylphenylsulfonyl)phenyl)sulfone) are preferred.
Methods for adding the antifoggants of the present invention to the light-sensitive materials of the present invention include the above-described methods for adding the reducing agents. The organic polyhalogen compounds are preferably added as fine solid particle dispersions.
Other antifoggants include mercury (II) salts described in JP-A-11-65021, paragraph number 0113, benzoic acid derivatives described in JP-A-11-65021, paragraph number 0114, salicylic acid derivatives represented by formula (Z) of JP-A-284399/2000 and formalin scavengers represented by formula (S) of JP-A-221634/2000.
In the present invention, the photothermographic materials may contain azolium salts for the purpose of fog prevention. The azolium salts include compounds represented by formula (XI) described in JP-A-59-193447, compounds described in JP-B-55-12581, and compounds represented by formula (II) described in JP-A-60-153039. Although the azolium salt may be added to any site of the light-sensitive material, it is preferably added to a layer on a side having the light-sensitive layer. More preferably, it is added to the organic silver salt-containing layer. The azolium salt may be added at any stage of the preparation of the coating solution. When added to the organic silver salt-containing layer, the azolium salt may be added at any stage from the preparation of the organic silver salt to the preparation of the coating solution, preferably from after the preparation of the organic silver salt to immediately before coating. The azolium salt may be added in any form such as a powder, a solution or a fine particle dispersion. Further, the azolium salt may be added as another solution in which it is mixed with an additive such as a sensitizing dye, a reducing agent or a color toning agent. In the present invention, the azolium salt may be added in any amount, but preferably in an amount of 1xc3x9710xe2x88x926 mol to 2 mol, more preferably 1xc3x9710xe2x88x923 mol to 0.5 mol, per mol of silver.
In the present invention, mercapto compounds, disulfide compounds or thione compounds can be added for inhibiting or accelerating development, improving the spectral sensitizing efficiency and improving shelf life (i.e., storage stability) before and after development. Such compounds are described in JP-A-10-62899, paragraph numbers 0067 to 0069, Jl?-A-10-186572 (compounds represented by formula (I) and specific examples described in paragraph numbers 0033 to 0052), EP-A-0803764, page 20, lines 36 to 56 and Japanese Patent Application No. 11-273670. Of these, mercapto-substituted heteroaromatic compounds are preferred.
In the present invention, phosphoryl group-containing compounds are preferably used, and phosphine oxides are particularly preferred. Specific examples thereof include triphenylphosphine oxide, tri -(4-methylphenyl)phosphine oxide, tri-(4-methoxyphenyl)phosphine oxide, tri-(t-butylphenyl)phosphine oxide and tri-(3-methylphenyl)phosphine oxide and trioctylphosphine oxide. The phosphoryl group-containing compounds of the present invention can be introduced into the light-sensitive materials in the same manner as in the reducing agents and the polyhalogen compounds. The phosphoryl group-containing compounds of the present invention are added preferably at a ratio (molar ratio) of 0.1 to 10, more preferably 0.1 to 2.0, still more preferably 0.2 to 1.0, based on the reducing agent.
Color toning agents are preferably added to the photothermographic materials of the present invention. The color toning agents are described in JP-A-10-62899, paragraph numbers 0054 to 0055, EP-A-0803764, page 21, lines 23 to 48 and JP-A-35631/2000. Preferred are phthalazinone, phthalazinone derivatives and metal salts thereof, or derivatives of 4-(1-naphthyl)phthalazinone, 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione; combinations of phthalazinone and phthalic acid derivatives (e.g., phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid anhydride); phthalazines (phthalazine, phthalazine derivatives or metal salts thereof, or derivatives of 4-(1-naphthyl)phthalazine, 6-isopropylphthalazine, 6-t-butylphthalazine, 6-chlorophthalazine, 5,7-dimethoxyphthalazine and 2,3-dihydrophthalazine); and combinations of phthalazines and phthalic acid derivatives (e.g., phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid anhydride). Combinations of phthalazines and phthalic acid derivatives are particularly preferred.
Plasticizers and lubricants which can be used in the light-sensitive layers are described in JP-A-11-65021, paragraph number 0117, and super contrast-increasing agents for formation of super high contrast images are described in JP-A-11-65021, paragraph number 0118, JP-A-11-223898, paragraph numbers 0136 to 0193, JP-A-284399/2000 (compounds of formulas (H), (1) to (3), (A) and (B)) and JP-A-347345/2000 (compounds of formulas (III) to (V), specific compounds: xe2x80x9ccompounds 21 to 24xe2x80x9d). Contrast-increasing accelerators are described in JP-A-11-65021, paragraph number 0102, and JP-A-11-223898, paragraph numbers 0194 to 0195. Methods for adding nucleating agents and the amount thereof are described in JP-A-11-223898, paragraph numbers 0182 to 0183.
For using formic acid or a formate as a strong foggant, it is added to a side having a light-sensitive silver halide-containing image formation layer preferably in an amount of 5 mmol or less, and more preferably in an amount of 1 mmol or less, per mol of silver.
When the nucleating agents are used in the photothermographic materials of the present invention, acids produced by hydration of diphosphorus pentaoxide or salts thereof are preferably used in combination therewith. The acids produced by hydration of diphosphorus pentaoxide or the salts thereof include metaphosphoric acid and salts thereof, pyrophosphoric acid and salts thereof, orthophosphoric acid and salts thereof, triphosphoric acid and salts thereof, tetraphosphoric acid and salts thereof, and hexametaphosphoric acid and salts thereof. Particularly preferred are orthophosphoric acid and salts thereof, and hexametaphosphoric acid and salts thereof. Specific examples of the salts are sodium orthophosphate, sodium dihydrogenorthophosphate, sodium hexametaphosphate and ammonium hexametaphosphate.
The acids produced by hydration of diphosphorus pentaoxide or the salts thereof may be used in a desired amount depending on performances such as sensitivity and fog. However, the amount thereof used (the amount thereof coated per m2 of light-sensitive material) is preferably from 0.1 mg/m2 to 500 mg/m2, and more preferably from 0.5 mg/m2 to 100 mg/m2.
The photothermographic material of the present invention may be provided with a surface protective layer for preventing adhesion of the image formation layer. The surface protective layers are described in JP-A-11-65021, paragraph numbers 0119 to 0120.
As a binder for the surface protective layer of the present invention, gelatin is preferred. However, the use of polyvinyl alcohol (PVA) is also preferred. Examples of the PVA includes PVA-105 (a completely saponified product), PVA-205 and PVA-335 (partially saponified products), and MP-203 (modified polyvinyl alcohol: the above names are names of commercial products manufactured by Kuraray Co., Ltd.). The amount of polyvinyl alcohol coated (per m2 of support) for every one protective layer is preferably from 0.3 mg/m2 to 4.0 mg/m2, and more preferably from 0.3 mg/m2 to 2.0 mg/m2.
In particular, when the photothermographic material of the present invention is used for application in printing in which changes in dimension cause trouble, it is preferred that a polymer latex is also used in the protective layer or a back layer. Such polymer latexes are described in Synthetic Resin Emulsions, edited by Taira Okuda and Hiroshi Inagaki, published by Kobunshi Kankokai (1978), Application of Synthetic Latexes, edited by Takaaki Sugimura, Yasuo Kataoka, Soichi Suzuki and Keiji Kasahara, published by Kobunshi Kankokai (1993) and Soichi Muroi, Chemistry of Synthetic Latexes, published by Kobunshi Kankokai (1970), and specific examples thereof include a methyl methacrylate (33.5% by weight)/ethyl acrylate (50% by weight)/methacrylic acid (16.5% by weight) copolymer latex, a methyl methacrylate (47.5% by weight)/butadiene (47.5% by weight)/itaconic acid (5% by weight) copolymer latex, an ethyl acrylate/methacrylic acid copolymer latex, a methyl methacrylate (58.9% by weight)/2-ethylhexyl acrylate (25.4% by weight)/styrene (8.6% by weight)/2-hydroxyethyl methacrylate (5.1% by weight)/acrylic acid (2.0% by weight) copolymer latex, and a methyl methacrylate (64.0% by weight)/styrene (9.0% by weight)/butyl acrylate (20.0% by weight)/2-hydroxyethyl methacrylate (5.0% by weight)/acrylic acid (2.0% by weight) copolymer latex. Further, as the binders for the protective layers, there may be applied combinations of polymer latexes described in EP1020760A, techniques described in JP-A-267226/2000, paragraph numbers 0021 to 0025, techniques described in EP1020760A, paragraph numbers 0027 to 0028, and techniques described in JP-A-19678/2000, paragraph numbers 0023 to 0041. The ratio of the polymer latex of the protective layer is preferably from 10% by weight to 90% by weight, and more preferably from 20% by weight to 80% by weight, based on the total binder.
The amount of the total binder (including a water-soluble polymer and the polymer latex) coated (per m2 of support) for every one protective layer is preferably from 0.3 mg/m2 to 5.0 mg/m2, and more preferably from 0.3 mg/m2 to 2.0 mg/m2.
The preparation temperature of the coating solutions for the image formation layers used in the present invention is preferably from 30xc2x0 C. to 65xc2x0 C., more preferably from 35xc2x0 C. to less than 60xc2x0 C., and still more preferably from 35xc2x0 C. to 55xc2x0 C. Further, the temperature of the coating solutions for the image formation layers immediately after addition of the polymer latexes is preferably maintained at a temperature of 30xc2x0 C. to 65xc2x0 C. Furthermore, it is preferred that the reducing agents and the organic silver salts are mixed before addition of the polymer latexes.
The organic silver salt-containing fluids or the coating solutions for the image formation layers used in the present invention are preferably so-called thixotropic fluids. The thixotropy means the property that the viscosity decreases with an increase in the shear rate. Although any instruments may be used for measurement of the viscosity in the present invention, an RFS fluid spectrometer manufactured by Rheometrics Far East Co., Ltd., is preferably used and measurements are made at 25xc2x0 C. Here, for the organic silver salt-containing fluids or the coating solutions for the image formation layers used in the present invention, the viscosity at a shear rate of 0.1 Sxe2x88x921 is preferably from 400 mPaxc2x7s to 100,000 mPaxc2x7s, and more preferably from 500 mPaxc2x7s to 20,000 mPaxc2x7s. Further, the viscosity at a shear rate of 1,000 Sxe2x88x921 is preferably from 1 mPaxc2x7s to 200 mPaxc2x7s, and more preferably from 5 mPaxc2x7s to 80 mPaxc2x7s.
Various kinds of systems exhibiting the thixotropy are known, and described in Course Rheology, edited by Kobunshi Kankokai, and Muroi and Morino, Polymer Latexes (published by Kobunshi Kankokai. For allowing fluids to exhibit the thixotropy, they are required to contain many fine solid particles. Further, for enhancing the thixotropy, it is effective to contain thickening linear polymers, to increase the aspect ratio by the anisotropic form of the fine solid particles contained, and to use alkali thickening agents and surfactants.
The photothermographic emulsion of the present invention is applied onto a support as one or more layers. For the single layer structure, the layer is required to contain the organic silver salt, the silver halide, a developing agent and the binder, and optionally, additional materials such as the color toning agent, an auxiliary coating agent (i.e., a coating aid) and other auxiliary agents. For the two-layer structure, a first emulsion layer (usually, a layer adjacent to the substrate) is required to contain the organic silver salt and the silver halide, and a second layer or both layers must contain some other components. However, a single emulsion layer containing all components and the two-layer structure comprising a protective top coat is also conceivable. The structure of a multicolor-sensitive photothermographic material may contain a combination of these two layers for each color, or all components in a single layer as described in U.S. Pat. No. 4,708,928. In the case of a multi-dye multicolor-sensitive photothermographic material, respective emulsion layers are generally kept distinguished from each other by using a functional or nonfunctional barrier layer between respective light-sensitive layers, as described in U.S. Pat. No. 4,460,681.
The light-sensitive layers used in the present invention can contain various kinds of dyes and pigments (e.g., C.I. Pigment Blue 60, C.I. Pigment Blue 64 and C.I. Pigment Blue 15:6) from the viewpoint of improvement in a color tone, prevention of the occurrence of interference fringes and prevention of irradiation. These are described in detail in WO98/36322, JP-A-10-268465 and JP-A-11-338098.
In the photothermographic material of the present invention, an antihalation layer can be provided on the side far away from a light source with respect to the light-sensitive layer.
The photothermographic materials generally have light-insensitive layers, in addition to the light-sensitive layers. The light-insensitive layers can be classified into four types: (1) a protective layer provided on the light-sensitive layer (on the side far away from the support), (2) an intermediate layer provided between the plural light-sensitive layers or between the light-sensitive layer and the protective layer, (3) an undercoat layer provided between the light-sensitive layer and the support, and (4) a back layer provided on the side opposite to the light-sensitive layer. The light-sensitive layer is provided with a filter layer as the layer of (1) or (2), and with an antihalation layer as the layer of (3) or (4).
The antihalation layers are described in JP-A-11-65021, paragraph numbers 0123 to 0124, JP-A-11-223898, JP-A-9-230531, JP-A-10-36695, JP-A-10-104779, JP-A-11-231457, JP-A-11-352625 and JP-A-11-352626.
The antihalation layer contains an antihalation dye having absorption at an exposure wavelength. When the exposure wavelength is in the infrared region, an infrared absorption dye is used, and in that case, a dye having no absorption in the visible region is preferably used.
When halation is prevented by using a dye having absorption in the visible region, it is preferred that the color of the dye does not substantially remain after image formation. For that purpose, a means of decoloring the dye by heat of heat development is preferably used, and particularly, it is preferred that a heat decoloring agent and a base precursor are added to the light-insensitive layer to allow it to act as an antihalation layer. These techniques are described in JP-A-11-231457.
The amount of the decoloring dyes added is determined depending on their purpose. In general, they are used in such an amount that an optical density (absorbance) exceeding 0.1 is given when measured at a desired wavelength. The optical density is preferably from 0.2 to 2. The amount of the dyes used for obtaining such optical density is generally from about 0.001 g/m2 to about 1 g/m2.
Such decoloring of the dyes allows the optical density after heat development to decrease to 0.1 or less. Two or more kinds of decoloring dyes may be used together in heat decoloring type recording materials or the photothermographic materials. Similarly, two or more kinds of base precursors may be used together.
In heat decoloring using such decoloring dyes and base precursors, it is preferred in terms of heat decoloring properties that they are used in combination with substances (e.g., diphenyl sulfone and 4-chlorophenyl(phenyl)sulfone) decreasing the melting point by 3xc2x0 C. or more by mixing with the base precursors as described in JP-A-11-352626.
In the present invention, for improving the variation of silver tone images with the elapse of time, a coloring agent having the absorption maximum at 300 nm to 450 nm can be added. Such coloring agents are described in JP-A-62-210458, JP-A-63-104046, JP-A-63-103235, JP-A-63-208846, JP-A-63-306436, JP-A-63-314535, JP-A-01-61745 and Japanese Patent Application No. 11-276751.
Such a coloring agents are usually added in an amount ranging from 0.1 mg/m2 to 1 g/m2, and preferably added to a back layer provided on the side opposite to the light-sensitive layer.
It is preferred that the photothermographic material of the present invention is a so-called single-sided light-sensitive material having at least one silver halide emulsion-containing light-sensitive layer on one side of the support and the back layer on the other side.
In the present invention, a matte agent is preferably added for improving the transferring properties. The matte agents are described in JP-A-11-65021, paragraph numbers 0126 to 0127. When indicated by the amount coated per m2 of light-sensitive material, the amount of the matte agent coated is preferably from 1 mg/m2 to 400 mg/m2, and more preferably from 5 mg/m2 to 300 mg/m2.
The matte degree of an emulsion surface may be any, as long as no white-spot unevenness occurs. However, the Bekk""s smoothness is preferably from 30 seconds to 2,000 seconds, and particularly preferably from 40 seconds to 1,500 seconds. The Bekk""s smoothness can be easily determined by the Japanese Industrial Standard (JIS) P8119, xe2x80x9cSmoothness Test Method of Paper and Paperboard with BeKk""s Testerxe2x80x9d and the TAPPI Standard T479.
In the present invention, the Bekk""s smoothness of the back layer is preferably from 10 seconds to 1,200 seconds, more preferably from 20 seconds to 800 seconds, and still more preferably from 40 seconds to 500 seconds.
In the present invention, the matte agent is preferably contained in the outermost surface layer, a layer which functions as the outermost layer, or a layer close to the outer surface, of the light-sensitive material, and preferably contained in a layer which functions as the so-called protective layer.
The back layers applicable to the present invention are described in JP-A-11-65021, paragraph numbers 0128 to 0130.
In the photothermographic materials of the present invention, the film surface pH before heat development processing is preferably 6.0 or less, and more preferably 5.5 or less. Although there is no particular limitation on the lower limit thereof, it is about 3. It is preferred from the viewpoint of reducing the film surface pH that the film surface pH is adjusted with organic acids such as phthalic acid derivatives, nonvolatile acids such as sulfuric acid, or volatile bases such as ammonia. In particular, ammonia is volatile and removable before the coating stage or heat development, so that it is preferred in that the low film surface pH is achieved. A method for measuring the film surface pH is described in JP-A-284399/2000.
A hardener may be used in each layer of the light-sensitive layer, the protective layer and the back layer of the present invention. Examples of the hardeners are described in T. H. James, THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION, pages 77 to 87, published by Macmillan Publishing Co., Inc. (1977), and multivalent metal ions described in ibid., page 78, polyisocyanates described in U.S. Pat. No. 4,281,060 and JP-A-6-208193, epoxy compounds described in U.S. Pat. No. 4,791,042 and vinylsulfone compounds described in JP-A-62-89048 are preferably used.
The hardeners are added as solutions, and the solutions are preferably added to the coating solutions for image forming layers from 180 minutes before coating to immediately before coating, preferably from 60 minutes before coating to 10 seconds before coating. However, there is no particular limitation on the mixing process and the mixing conditions, as long as the effects of the present invention are sufficiently manifested. Specific examples of the mixing processes include a mixing process using a tank designed so that the average residence time calculated from the flow rate of the solution added and the amount of the solution supplied to a coater becomes a desired time, and a process using static mixers described in N. Harnby, M. F. Edwards and A. W. Nienow, translated by Koji Takahashi, Liquid Mixing Techniques, chapter 8, published by Nikkan Kogyo Shinbunsha (1989).
Surfactants applicable to the present invention are described in JP-A-11-65021, paragraph number 0132, solvents in the same, paragraph number 0133, supports in the same, paragraph number 0134, antistatic or conductive layers in the same, paragraph number 0135, methods for obtaining color images in the same, paragraph number 0136, and lubricants (i.e., sliding agents)in JP-A-11-84573, paragraph numbers 0061 to 0064 and EP1045284A, paragraph numbers 0049 to 0062.
As transparent supports, there are preferably used polyester films, particularly polyethylene terephthalate films subjected to heat treatment within the temperature range of 130xc2x0 C. to 185xc2x0 C. for relaxing internal strain remaining in the films at biaxial stretching to remove heat shrinkage strain generated in heat development processing. In the case of photothermographic materials for medical application, the transparent supports may be either colored with blue dyes (for example, dye-1 described in the example of JP-A-8-240877), or not colored. It is preferred that undercoating techniques of water-soluble polyesters described in JP-A-11-84574, styrene-butadiene copolymers described in JP-A-10-186565 and vinylidene chloride copolymers described in EP1045284A, paragraph numbers 0063 to 0080 are applied to the supports. Further, techniques described in JP-A-56-143430, JP-A-56-143431, JP-A-58-62646, JP-A-56-120519, JP-A-11-84573, paragraph numbers 0040 to 0051, U.S. Pat. No.5,575,957 andJP-A-11-223898, paragraph numbers 0078 to 0084 can be applied to the antistatic layers and undercoating.
The photothermographic materials are preferably of a mono-sheet type (a type in which images can be formed on the photothermographic materials without the use of other sheets, such as image receiving materials).
Anti-oxidizing agents, stabilizers, plasticizers, ultraviolet absorbers and coating aids may be further added to the photo thermographic materials. Various additives are added to either the light-sensitive layers or the light-insensitive layers. For these additives, reference can be made to WO98/36322, EP-A-803764, JP-A-10-186567 and JP-A-10-18568.
The photothermographic materials of the present invention may be applied by any methods. Specifically, various coating operations including extrusion coating, slide coating, curtain coating, dip coating, knife coating, flow coating and extrusion coating using a hopper described in U.S. Pat. No. 2,681,294 are used. Extrusion coating described in Stephen F. Kistler and Petert M. Schweizer, LIQUID FILM COATING, pages 399 to 536, published by CHAPMAN and HALL (1997) or slide coating is preferably used, and slide coating is particularly preferably used. Examples of the shapes of slide coaters used in slide coating are shown in ibid., FIG. 11b. on page 427. Two or more layers can be formed at the same time by methods described in ibid., pages 399 to 536, U.S. Pat. No. 2,761,791 and GB-837,095, as so desired.
Techniques which can be used in the photothermographic materials of the present invention are also described in EP-A-803764, EP-A-883022, WO98/36322, JP-A-56-62648, JP-A-58-62644, JP-A-9-281637, JP-A-9-297367, JP-A-9-304869, JP-A-9-311405, JP-A-9-329865, JP-A-10-10669, JP-A-10-62899, JP-A-10-69023, JP-A-10-186568, JP-A-10-90823, JP-A-10-171063, JP-A-10-186565, JP-A-10-186567, JP-A-10-186569 to JP-A-10-186572, JP-A-10-197974, JP-A-10-197982, JP-A-10-197983, JP-A-10-197985 to JP-A-10-197987, JP-A-10-207001, JP-A-10-207004, JP-A-10-221807, JP-A-10-282601, JP-A-10-288823, JPA-10-288824, JP-A-10-307365, JP-A-10-312038, JP-A-10-339934, JP-A-11-7100, JP-A-11-15105, JP-A-11-24200, JP-A-11-24201, JP-A-11-30832, JP-A-11-84574, JP-A-11-65021, JP-A-11-109547, JP-A-11-125880, JP-A-11-129629, JP-A-11-133536 to JP-A-11-133539, JP-A-11-133542, JP-A-11-133543 and JP-A-11-223898.
Although the photothermographic materials of the present invention may be developed by any methods, the photothermographic materials exposed imagewise are usually developed by elevating the temperature thereof. The developing temperature is preferably from 80xc2x0 C. to 250xc2x0 C., and more preferably from 100xc2x0 C. to 140xc2x0 C. The developing time is preferably from 1 second to 180 seconds, more preferably from 10 seconds to 90 seconds, and particularly preferably from 10 second to 40 seconds.
As the heat development system, a plate heater system is preferred, and as the heat development system according to the plate heater system, a method described in JP-A-11-133572 is preferred. In this method, a heat development apparatus giving visible images by contacting the photothermographic material having latent images formed with a heating means in a heat development unit is used, wherein the heating means comprises a plate heater, a plurality of press rollers are arranged along one side of the plate heater, facing thereto, and the photothermographic material is allowed to pass between the press rollers and the plate heater to conduct heat development. It is preferred that the plate heater is divided into 2 to 6 steps and the temperature is decreased by about 1xc2x0 C. to about 10xc2x0 C. at a leading edge portion thereof. Such a method is also described in JP-A-54-30032, and water and an organic solvent contained in the photothermographic material can be removed outside the system. Further, changes in the support form of the photothermographic material caused by rapid heating thereof can also be inhibited.
Although the light-sensitive materials of the present invention may be exposed by any methods, laser light is preferably used as an exposure light source. Preferred examples of the lasers used in the present invention include a gas laser (Ar+ or Hexe2x80x94Ne), a YAG laser, a dye laser and a semiconductor laser. Further, a semiconductor laser and a second harmonic generating element can also be used in combination. Preferred is a red- to infrared-emitting gas laser or a semiconductor laser.
Laser imagers for medical application provided with exposure units and heat development units include a Fuji medical dry laser imager, FM-DPL. FM-DPL is described in Fuji Medical Review, No.8, pages 39 to 55, and needless to say, this technique can be applied as the laser imager for the photothermographic material of the present invention. Further, this can also be applied as the photothermographic material for the laser imager in an xe2x80x9cAD networkxe2x80x9d proposed by Fuji Medical System as a network system adapted to the DICOM standard.
The photothermographic materials of the present invention form black and white images according to silver images, and preferably used as photothermographic materials for medical diagnosis, photothermographic materials for industrial photography, photothermographic materials for printing and photothermographic materials for COM.